This is the same problem as a number of other have reported, e.g.
Failed to fetch URL https://dl-ssl.google.com/android/repository/addons_list-1.xml, reason: Connect
i got the same problem today, and i think is because the china GFW block me. bad ass.. ok,try this,sdk manager -> tools them use proxy, i tried ,
proxy server: www.google.com.hk (i am in china,try www.google.com if other country)。
proxy port : 80
and choose Force https://.... sources bala bala
then click packages -> reload,the problem is gone. i find this when i google this issue.